This invention relates to titanium dioxide-based chromatic pigments useful as a colorant of paints, printing inks, plastics, cosmetics and the like.
Titanium dioxide particles are well-known as a white pigment and have been used in the paint, plastics, cosmetics and many other industries. The pigment grade TiO.sub.2 particles generally have a mean particle size of about 0.2-0.3 .mu.m. Finer particles of TiO.sub.2 having a mean particle size less than 0.1 .mu.m exhibit different optical properties from the TiO.sub.2 pigments. They are almost colorless or transparent to visible light but selectively block the passage of UV light therethrough. Accordingly, they find uses as UV blocking agents rather than chromatic pigments in the paint, plastics, cosmetics and other industries. In addition, U.S. Pat. No. 4,753,829 discloses the incorporation of TiO.sub.2 microparticles into the base coat of multi-layer metallic coatings to promote "down-flop" effect.
TiO.sub.2 based chromatic pigments have been known including those disclosed in U.S. Pat. No. 2,257,278 and Japanese Patent Publication No. 25685/72. They are generally solid solutions of coloring oxides of metals such as Sb, Ba, Ni and Co in a TiO.sub.2 lattice. These pigments are produced by intimately mixing TiO.sub.2 and the coloring metal oxides or oxide precursors, calcining the mixture at a temperature of 1000.degree.-1300.degree. C., cooling and grinding the resulting products. Pigments thus produced are very hard and it is difficult to grind them to a mean particle size of less than 0.1 .mu.m.
Accordingly, needs exist for chromatic pigments useful as a colorants of paints, plastics, cosmetics and the like while retaining at the same time most of beneficial properties of TiO.sub.2 microparticles such and UV blocking and down flop promoting properties.